Micropollutants in water often are hormones that accumulate in the environment and may have negative impacts on humans and animals. Researchers of Karlsruhe Institute of Technology (KIT) and Leibniz Institute of Surface Engineering (IOM) in Leipzig have now developed a process for the photocatalytic degradation of these pollutants when they flow through polymer membranes. It is presented in Nature Nanotechnology. Irradiation with light triggers a chemical reaction, as a result of which steroid hormones are degraded on the membranes coated with titanium dioxide.